This study will test the hypotheses that oral dexamethasone (8 mg, PO BID for 5 days) alters hepatic and/or intestinal cytochrome P450 3A4 (CYP3A4) activity in healthy volunteers. The CYP3A4 pathway metabolizes approximately half of orally administered medications. Dexamethasone is administered to a large number of cancer patients as part of their chemotherapy regimen, to decrease the likelihood of chemotherapy induced emesis or other chemotherapy associated side effects. Human heptocyte and a small amount of clinical data demonstrate CYP3A4 activity is induced by dexamethasone. Alterations in CYP3A4 activity can affect the bioavailability and clearance of antineoplastics metabolized by this pathway, therefore potentially altering their systemic exposure, efficacy and/or toxicity.